1. Technical Field of the Invention
This invention relates to a monitoring display system to be installed in an operating room of a construction machine, for example, of a hydraulic power shovel to keep an operator informed of various operating conditions of the machine and information relating to working site or environment.
2. Prior Art
As well known in the art, hydraulic power shovels, typical of construction machines, are provided with an engine-driven hydraulic pump to supply pressure oil to hydraulic cylinders and motors or hydraulic actuators in various operating parts of the machine. The various operating parts of a machine are controlled by an operator by manipulation of control levers or other control means provided in an operating room or cab, for example, for a digging operation.
Generally, various indicators and instruments are provided in a cab of a construction machine to let an operator recognize operating conditions of the machine. For instance, indicators in the cab include an engine speedometer, fuel meter, cooling water temperature indicator, operating oil temperature indicator and hour meter. In addition, there are provided other indicators which show information needed for safe operation of the machine, for example, information whether or not a gate lock lever is in a correct position. Further, the operator is allowed to recognize the starter key position and the type of attachment which is currently attached on a front working mechanism.
Some construction machines are already furnished with a liquid crystal display monitor within a cab to indicate a diversity of information related with machine operations. By the use of a monitor display of compact construction, the operator can be constantly informed of exact operating conditions of the machine. In this connection, for the purpose of assisting an operator to operate a machine in safe conditions, there has been developed and introduced a monitor display which is arranged to display on a monitor screen picture images of a rear view monitor camera which is mounted at a rear side position of the machine to take rear views in dead angles from an operator in a cab.
In the case of a construction machine employing a rear view monitor system to display picture images of a rear view monitor camera, it becomes necessary to install a rear view monitor display in a cab along with a monitor display which displays picture images of instrumentation data, despite the likelihood of obstruction of the operator's view field in the forward direction and distraction of the operator's attention from instrumentation data. Therefore, it has been the general practice to provide in a cab a single monitor display which is switchable to display selectively either picture images of instrumentation data or picture images of a rear view monitor camera. However, this type of machine monitoring system is not desirable because an operator has to switch the monitor display from time to time during machine operations. In order to solve these problems, disclosed in Japanese Laid-Open Patent Application H11-286971 is a machine monitor display which is arranged to display picture images of minimum necessary instrumentation data and picture images of a rear view monitor camera in divided picture image display areas of a monitor screen.
In a case where two different kinds of information are displayed separately in divided image display areas of a monitor screen as mentioned above, each one of the picture image display areas is cut smaller. Namely, enlargement of a camera image display area would necessarily result in not only curtailment and lower visibility of picture images in other instrumentation data display areas but also restrictions of instrumental data to be displayed. On the contrary, enlargement of the instrumental data display area would result in curtailment of the camera image display area, that is to say, lower visibility of picture images from a camera. Thus, a monitor screen with divided image display areas has an inherent problem of low visibility of one or both picture images in two divided display areas.
Of the two kinds of picture images to be displayed on a monitor screen, a camera image is not always viewed with great concern in its entire display area. For example, picture images from a rear view monitor camera are viewed mainly when staring a machine in reverse direction or when turning an upper swing structure of the machine. In other operational scenes or in other situations, degradations in quality of camera images would not give rise to any problem in particular. Therefore, in a total camera image display area, practically other information can be overlapped in regions of less concern as long as a machine operator can get a through view of camera images behind overlapped picture images of other information.